Guy Shishio lives as a cyborg after a near-fatal encounter with alien invaders two years ago. Now part of the Gutsy Geoid Guard, he pilots the massive robot GaoGaiGar to defend Tokyo against Zonder creatures emerging from beneath the Earth's surface. Alongside a robotic lion named Galeon and a young boy capable of purifying these threats, Guy fights to prevent the total destruction of humanity. The year is 2005, and the battle for survival has already begun.